Patient identification method for x-ray film user-interfaces

ABSTRACT

A method for identifying digitized X-ray films using the label that is “burned” on such films. The label is digitized and can be used as a single identifier for the corresponding X-ray film image. The digitized label can be displayed such as to be readable by the user thereby allowing the selection and retrieval of the image. The digitized label can also be associated with image analysis results, such as CAD analysis, performed on the corresponding X-ray film image allowing easy retrieval of such results.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority on U.S. provisional application Ser.No. 60/408,079, filed Sep. 4, 2002 entitled “Patient identificationmethod for CAD user-interfaces”.

TECHNICAL FIELD

This invention relates to the field of X-ray film identification andmore particularly to identification of digitized X-ray films in computeruser interfaces.

BACKGROUND OF THE INVENTION

X-ray films can be scanned by a film digitizer, and converted intodigital format. Digitized films can then be stored for future retrievalor analyzed with imager analysis algorithms such as Computer AidedDetection (CAD). Film digitizers are available from, for example, Canon,Howtek, Kodak, or Vidar. The film digitizer is, connected to a standardcomputer and a standard user interface controls scanning, identifying,and storing the digitized films as images on disk. Standard userinterfaces for digitizer control, including quality control, errordetection, and error recovery, are available from Vidar, Applicare, orMerge.

In the diagnosis process, quick and reliable identification of the filmis required to increase the efficiency of the process and reduce therisk of errors associated with misidentification. Furthermore digitizedX-ray films are often analyzed with software applications such as CADand reliable association of the CAD results with the correspondingdigitized X-ray film is very important.

In a typical scenario, the radiologist normally reads the filmmammograms on an alternator or on a light box. Suspicious findings arenoted by the radiologist, and recorded in a medical report. However, anon-zero percentage of cancers are typically missed by radiologists. Todecrease the rate of false negative, a second radiologist may read thefilms, and the results of both radiologists are compared.

The results of CAD can be used in much the same way as a secondradiologist. In one scenario, also referred to as “second read withCAD”, the radiologist first reads the films without the aid of acomputer. Once the radiologist has noted her findings, she reviews thesuspicious areas identified by CAD analysis, for example on a monitor asan overlay over the digitized versions of the mammogram, or printed onpaper. The suspicious areas may confirm the findings of the radiologist.Or, the radiologist may be prompted to re-examine areas she had notfound to be suspicious, but which were highlighted by the computer.

In another scenario, also referred as “cued read with CAD”, theradiologist may read the films and review the CAD results at the sametime, moving back and forth between them using the CAD results to “cue”her reading.

In either scenario, it is important to ensure that the CAD results areproperly associated with the X-ray films to ensure correctidentification of the results and avoid “mix-up” of the films and CADresults. Commercial products currently use a number of methods for toachieve this.

For example a bar code system can be used. When films are digitized, aseparator sheet of the same approximate size of the films is alsoscanned. It serves as a separator between the films of one case and thefilms of the next case. A bar code is printed on the separator sheet.The digitization system reads the bar code, and digitally associates itwith the images. The operator enters no patient name, accession number,or other identifier, the bar code information is the identifier of thecase only the numerical identifier corresponding to the bar code (anumber) identifies the patient. After the digitization, the films arereplaced in the jacket, together with the separator sheet with the barcode.

When the films are hung on the alternator, a bar code reader is used toscan the bar code on separator sheets. The alternator contains acomputer and logic to associate the CAD results with a particularalternator position (that of the corresponding X-ray films). That way,the proper digital images and CAD results are displayed on themini-monitors integrated into the alternator depending on the alternatorposition. The numerical identifier corresponding to the bar code(together with the alternator position) identities the patient.

This method is deficient in that radiologists and other medicalpersonnel use patient names and patient record identifiers to identifypatients, and cross-correlate patients to other medical information,reports, requisitions, and the like. Since the CAD results areidentified only with a barcode and its associated numerical identifier,association of patient names or records with CAD results involves anindirect and unreliable cross-referencing method from CAD results to barcode to patient name. This method is not only inconvenient and timeconsuming, but also prone to errors.

In other systems a bar code sticker is affixed to each individual film(the sticker includes the orientation information of each individualfilm). The digitizer uses the bar code to associate it with the films ofthe patient. When the films are reviewed, a bar code reader is used toread the bar code stickers on the films, and the appropriate images aredisplayed on a monitor, together with the CAD results. In this systemthe CAD results are not associated with alternator positions. Thismethod is equally deficient in that the only mechanism to correlate CADresults with a patient name is to cross-correlate the bar code numbersof the CAD results with a bar code label affixed to an X-ray film.

Yet another method is, described in “Hybrid display for simultaneousside-by-side review of radiographs”, U.S. Pat. No. 5,748,173. In thedescribed system, patient information in the form of a name or a patientnumber is obtained directly from the film that is placed on a view box(alternator or light box) using a bar code scanner or a CCD camera. Thismethod is also deficient in that the CAD results have to be identifiedby other means with the patient name or patient number before they canbe recalled with the method described here.

Other strategies have also been used to identify X-ray films. Forexample the operator can enter the patient name and identification. Thepatient name is then digitally associated with the digitized images.When a case is reviewed, the radiologist enters the patient name in acomputer, and the appropriate images and CAD results are displayed.Alternatively, the radiologist can select the patient name from a list.A disadvantage of this method is that the patient name has to be enteredmanually at the time of digitization, and potentially again at the timeof review.

SUMMARY OF THE INVENTION

In one aspect of the present invention there is provided a methodwhereby human-readable patient information on a label is automaticallyobtained from digitized X-ray film. This human-readable patientinformation is then used to identify the corresponding X-ray film. Inone aspect of the invention the label of a digitized X-ray film isdigitally extracted and associated with the corresponding film anddisplayed such as to be readable by a user. This advantageously avoidsthe need to identify the film by indirect means such as by scanning abar code affixed to the film or by having to enter the name oridentification number of a patient and therefore overcomes severaldisadvantages of the prior art.

In one embodiment of the invention the digitally extracted label can beenhanced to increase the contrast or to remove textured background tofacilitate reading by the user of the alpha-numeric informationcontained in the label.

The digitized label may also be associated with results of X-ray filmimage analysis such as Computer Aided Detection Analysis (CAD). Thehuman-readable label may be used in user-interfaces related to CAD,including but not limited to, quality control of digitized X-ray films,worklist preparation for review of X-ray films with CAD, selection ofCAD results for the purposes of review of X-ray films, display of CADresults during or after review of X-ray films, and documentation of CADresults in electronic form.

In a further embodiment, the digitized label can be used toautomatically group digitized X-ray films belonging to the same patient.This can be achieved by digitally comparing the labels of differentfilms using image comparison techniques and using pre-determinedcorrelation criteria to relate the films.

In yet a further embodiment, sub-labels can be digitally extracted froma label and associated with corresponding X-ray film images and or imageanalysis results such as CAD. By enabling the identification of imagesusing selected information from the label, the method provides increaseflexibility for retrieving desired films.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention will becomeapparent from the following detailed description, taken in combinationwith the appended drawing, in which:

FIG. 1 is a schematic representation of the identification process usingdigitized X-ray film label according to an embodiment of the invention;

FIG. 2 is a schematic representation of the label enhancement processaccording to an embodiment of the invention;

FIG. 3 is a schematic representation of the association and displayingof labels with CAD results according to an embodiment of the invention;

FIG. 4 is a schematic representation of the digital extraction anddisplaying of sub-labels according to art embodiment of the presentinvention;

FIG. 5 is a schematic representation of the labels lists to select andretrieve corresponding X-ray film imagery according to an embodiment ofthe invention; and

FIG. 6 is a schematic representation of label/film display combinationsaccording to possible embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Individual X-ray films are labeled with patient information that is“burned” into the film. This is accomplished with a device that exposesa small (approximately 1×2 inches) area of the film with alpha-numericinformation that typically lists the patient name, birth date,identification number, accession number, and the name or identifier ofthe technologist;

Depending on the institution and the devices, the patient informationarea may be in the same place on all films, or it may vary. It may be onthe edge of the film, or it may be somewhere in the background areaoutside of the anatomical feature shown on the film. It may have blackon white text, or white on black text, it may be typed, or computergenerated, and the fields and their alignment may differ frominstitution to institution, imaging device to imaging device, and examto exam.

In one aspect of the present invention, the area of patient information(i.e. the label) can be used as the digital identifier of a patient, inlieu of any other digital identifier. Thus there is provided a methodand system for identifying digitized X-ray films comprising a labelwhich contains alpha-numeric information related to the patient andother information such as but not limited to conditions of exposure ofthe film.

Referring to FIG. 1, a digitized image of the label 11 is obtained fromX-ray film 10 and is digitally associated, in look-up table 12, with thecorresponding digitized X-ray film. The digitized label 14 is displayedon a user interface 16 such as computer screen to allow the user toidentify the corresponding film using the alpha-numeric information onthe label. The image of the label can be displayed alone orsimultaneously with the X-ray film image.

In some cases the digitally extracted label may have texturedbackground, be blurred or the contrast may not be important enough toallow easy reading of the information by the user. In these cases thelabel can be digitally enhanced. By label enhancement it is meant thatcertain procedures are performed to, for example, remove texturedbackground, increase the contrast between the alpha-numeric charactersand the background and enlarge the image. These procedures are wellknown in the art. Thus, and by referring to FIG. 2 the label 14 can beenhanced into an enhanced label (EL) 20 and digitally associated inlook-up table 22 with either the corresponding X-ray film or thecorresponding (non-enhanced) label or both. It will be appreciated thatif the EL is associated with its corresponding label it can therefore beindirectly associated with the corresponding digitized X-ray film.

Image analysis algorithms such as CAD algorithms can be applied to thedigitized films, and the results can be associated with the label (orEL) and corresponding X-ray film images (FIG. 3). The patientinformation area (label or EL) serves as the unique identifier of thepatient, the images, and the image analysis results. Thus the label canbe displayed simultaneously with the X-ray film image and the CADresults or, alternatively, the label can be displayed with the imageanalysis results alone.

In a preferred embodiment the digitized label is obtained byautomatically locating and digitally extracting it from the remainder ofthe digitized X-ray film. To that effect, pattern recognition and imageprocessing methods, which are known in the art, can be used. Suchmethods may include but are not limited to edge detection and texturesegmentation. For example, in edge detection, the gradient of pixelsintensity of an image is determined and used to identify a portion ofthe image wherein the gradient corresponds to a predetermined gradient,characteristic of the presence of the label. The extracted digital labelwill be used to identify the images of a case.

In another aspect of the invention, the user is presented with a userinterface to interactively identify the location of the patientinformation area, and this area is then digitally extracted.

In yet another aspect of the invention, standard locations of thepatient information area in films of different orientation are stored onthe computer disk. Depending on the orientation of the film, thestandard location of the patient information area on the film can belooked up, and the patient information area can be extracted from thatarea.

It should be noted that the extraction of the patient information areacorresponds to selection of a sub-image in the digitized X-ray image,but not necessarily actual elimination of the remainder of the image(the complement of the sub-image). As is familiar to those skilled inthe art, the extraction of a sub-image can be achieved both by copyingthe pixel elements of a sub-image into a new image buffer, andmaintaining the sub-image as a separate image; or by identifying arectangular region in the original image, and representing the newsub-image in the form of a reference to the original image and theco-ordinates of the rectangular region in that original image. Theactual representation of the extracted area and sub-image is largelydetermined by software architecture and design of a particularimplementation of the present invention.

In this respect, and referring to FIG. 4, the label 14 (or EL) may besubdivided into one or more sub-labels 40. As described above for thelabels, the sub-labels can be digitally extracted and associated withthe corresponding label, digitized X-ray film and/or image analysisresults in a look-up table 42. Since more than one sub-label can beextracted from the label, different sub-labels may correspond to thesame label of X-ray film image 44 or image analysis results. A sub-labelmay comprise the name of the patient or the voltage used during exposureof the film or orientation information (for example,medio-lateral-oblique (MLO) or cranio-caudal (CC)), and which side ofthe breast was imaged (Left or Right) or any other information containedin the label. It may also contain a combination or such information. Thesubdivision of the label advantageously allows the user to recall one ormore film images based on information other than information that isexclusive to one patient such as the name of the patient.

A label detection application can be assigned to a digital imageaccording to the method described in co-pending application U.S. Ser.No. 10/205,599 incorporated herein by reference. The method comprisesthe steps of: selecting a label acquisition model from a plurality ofacquisition models based on at least one attribute of the digital label;and selecting a label detection application from a plurality of labeldetection applications using the selected label acquisition model.

In some embodiments, selection of an acquisition model may include thesteps of: obtaining at least on one attribute of the digital label, andperforming a search to identify the acquisition model using the obtainedattributes. The label detection application may be selected by obtaininginformation concerning the digital label in accordance with the selectedacquisition model and performing a search to identify the labeldetection application using at least the obtained information.

An example of a system that supports the assignment of a label detectionapplication is also described in co-pending application U.S. Ser. No.10/205,599 incorporated herein by reference. The system includes a caseinput system for selecting an acquisition model from a plurality ofacquisition models, based on at least one attribute of the digitallabel, and for selecting a label detection application from a pluralityof label detection applications using the selected acquisition model.

The system may further include an algorithm server for retrieving andapplying the selected label detection application to the digital label.

It will be appreciated that other approaches car be used to assign alabel detection application to a digitized X-ray film. For example theapplication could be a default application.

In diagnosis procedures, such as screening mammography, almost the sameinformation is applied to all films of the same patient, although inmany cases information pertaining to the individual film, such as X-raycurrent and orientation is also displayed on the label. Therefore, thelabels may differ in some minor aspects.

Thus, all films for the same patient contain an area of about 1×2 inchesthat is very similar in content, but may be subject to variations inexposure, noise, and other artifacts. Hence the patient label extractedfrom one image of the case may be used to represent all images of thecase, or all images of the patient. Thus in another aspect of the methodof the present invention the images belonging to a patient canautomatically be grouped using the digitized alpha-numeric informationof the label. For grouping purposes, films of several patients areloaded into a digitizer, and the films are scanned and converted intodigital form. No separator sheets are used, and films of severalpatients can be mixed. The area of patient information is automaticallyidentified on each film, and correlated with the correspondinginformation on other films. Pairs of films with high correlation valuesfor these patient information areas are considered to belong to the samepatient, and pairs with low correlation values belong to differentpatients. Alternatively, character recognition can be performed on theidentification area, and the patient name and other information isobtained directly in alpha-numerical form. This way, the patient namecould be obtained and used as the identifier of a film, and films ofeach patient can be grouped based on the patient name.

Similarity between two films can be determined by comparing the patientinformation areas (labels) of the two films. Correlation methods, knownto those skilled in the art, including but not limited to shift/rotationand intensity/contrast variations can be used to determine thesimilarity. A predetermined high correlation indicates that the twofilms belong to the same patient and a predetermined low correlationindicates that the two films belong to different patients.

Typically, films of consecutive patients are placed in the input tray ofthe digitizer. Films of one patient are grouped together, followed bythe films of the next patient, etc. Therefore, the correlation methodwill be applied to pairs of consecutive films only. In most cases, therewill be groups of four films, which exhibit a high correlation, and thusbelong to one patient. Correlation between the last film of one patientand the first film of the next patient will be poor. Then, the fourfilms of the next patient will exhibit high mutual correlation thereforeenabling the grouping of the films that belong to the same patient.

Alternatively, it is also possible to scan films of multiple patientswithout grouping films of individual patients together. In that case,correlation is preferably performed between all pairs of individualfilm.

The digitized labels of each film on in a group can bet digitallyassociated with any or all digitized films belonging to this group.Therefore it is possible to display all the digitized film in a group byselecting only one label. It will be appreciated that any other displaycombination (1 label 2 films, 1 label 3 films 2 labels 3 films etc.) ispossible within one group.

The method is not limited to groups of four films per patient. Anynumber of films per patient can be treated and identified with thecorrelation method.

Using the method of the present invention, an X-ray film image can beselected and retrieved from a plurality of stored images. Now referringto FIG. 5, the labels (or EL or sub-labels) corresponding to all or apredetermined number of the stored films can be displayed on userinterface to allow the user to select one or north desired X-ray film.It will be appreciated that image analysis results, such as CAD, canalso be retrieved according to this embodiment. For example, the labels(or EL or sub-labels) of all available patients can be displayed on acomputer monitor in a list. A technologist creates a “worklist” of CADresults (for example, corresponding to the order of x-ray films on analternator or light box) through manipulation of digital patientidentifiers (i.e. the labels) in a list displayed at the user interface.For example, this could be a scrollable list, and “cut-and-paste” withinthe list could be used to change the order. Or, two lists can be used,one for all available patients, and one for the worklist. Thetechnologist can move the digital identifiers from one list to the otherin the desired order using a mouse or a touch screen user interface forexample. Displaying of the labels in a list also enables the user todirectly select the name of one or several desired patients without theneed to cross-refer the name of the patient with an ID number or to scana bar code on a film.

FIG. 6 shows possible embodiments of label/film displays wherein thelabel can be displayed simultaneously with the digitized film and/orwith image analysis results. It will be appreciated that other displayarrangements/combinations are possible.

Further, the digital labels could be used to arrange cases into asequence, for example to create an ordered worklist of patients to bereviewed by a radiologist, as the films of the patient are hung on analternator.

Also, the digital labels could be used to arrange that cases into atwo-dimensional table, corresponding to the layout of the cases on alight box.

During the reading process, the CAD results are displayed on a monitorin proximity to the alternator or view box. In typical workflow, the CADresults are displayed after (for a “second read scenario”) theradiologist has analyzed the images, to obtain prompts for additionalsuspicious areas. After review of the films, the radiologist selects thecorresponding patient information area on the monitor (using a mouse, ora touch screen, for example). Next, the corresponding images and CADresults are displayed on the same monitor. This is possible because theimages and CAD results are digitally associated with the patientinformation area.

The digitally extracted label can be used whenever the digital image isdisplayed on a monitor or printed on media. Furthermore, by visuallyassociating the digital image with the digitally extracted label usinggraphics, tabular alignment, color coding, or any other such method, theuser can recognize that the label and its associated image are indeedrelated, and will thus be able to identify the image as belonging to aparticular patient.

It will be appreciated that the above described method of identifyingX-ray images of a patient can be used on the digitization station, whereimages are displayed after digitization for quality control purposes oron a CA) results display station, which is used by radiologists toreview areas that may have been deemed suspicious of disease by CAD.

In another aspect of the invention there is provided a system foridentifying and retrieving digitized X-ray films having a label, thesystem comprises: an X-ray film digitizer for generating a digital imageof each X-ray film; processor means for determining a position of thelabel on the digital image of the X-ray film; processor means fordigitally extracting an image of the label from the digital image of thex-ray film; processor means for digitally associating the image of thelabel with the digitized image of the X-ray film; a screen fordisplaying the label. The system may also comprise a processor means fordigitally associating the label with image analysis results of acorresponding digitized image of the X-ray film and processor means foranalyzing the images of a plurality of labels.

The system may further comprise means for displaying images of one ormore labels, user interface means for permitting a user to select one ofthe displayed labels, processor means for retrieving a digitized imageof an X-ray film associated with the selected label and display meansfor displaying the retrieved digitized images of the X-ray films forexamination by the user.

The embodiments of the invention described above are intended to beexemplary only. The scope of the invention is therefore intended to belimited solely by the scope of the appended claims.

1. A method for identifying a digitized x-ray film comprising at leastone label the method comprising the steps of: (i) obtaining a digitalimage of said label; (ii) digitally associating said digitized image ofthe label with said digitized x-ray film; and (iii) displaying saiddigital image of said label thereby allowing a user to identify saiddigitized x-ray film.
 2. The method as claimed in claim 1 furthercomprising the step of selecting said label to display said associateddigitized x-ray film.
 3. The method as claimed in claim 1 furthercomprising the step of digitally enhancing said image of the label priorto displaying said image of the label.
 4. The method as claimed in claim3 wherein said step of digitally enhancing comprises removing texturedbackground and increasing contrast between background and alpha-numericcharacters in said image of the label.
 5. The method as claimed in claim1 further comprising the step of digitally associating the label with acorresponding image analysis result of the digitized x-ray film.
 6. Themethod as claimed in claim 5 wherein said image analysis is a ComputerAided Detection (CAD) analysis.
 7. The method as claimed in claim 2wherein said image of said label is displayed simultaneously with saiddigitized x-ray film.
 8. The method as claimed in claim 5 wherein saidimage of said label is displayed simultaneously with said image analysisresult.
 9. The method as claimed in claim 5 wherein said image of saidlabel in displayed simultaneously with said image analysis result andsaid digitized x-ray film.
 10. The method as claimed in claim 1 whereinsaid step of obtaining a digital image of the label comprises: (i)determining position of said label on said film; and (ii) digitallyextracting said image of said label.
 11. The method as claimed in claim10 wherein said step of determining is performed automatically.
 12. Themethod as claimed in claim 11 wherein said step of determining positionis performed using a method selected from edge detection and texturesegmentation.
 13. The method as claimed in claim 10 wherein said step ofdetermining is performed by a user.
 14. A method for retrieving, from aplurality of digitized x-ray films, a digitized x-ray film said filmcomprising at least one label, the method comprising the steps of: (i)obtaining a digital image of said label; (ii) digitally associating saiddigitized image of the label with said digitized x-ray film; (iii)displaying a plurality of labels each associated with a digitized x-rayfilm; and (iv) selecting a label from said plurality of labels toretrieve said digitized x-ray film.
 15. The method as claimed in claim14 further comprising the step of displaying said x-ray film.
 16. Themethod as claimed in claim 14 further comprising the step ofdigitally-enhancing said image of the label prior to displaying saidimage of the label.
 17. The method as claimed in claim 16 wherein saidstep of digitally enhancing comprises removing textured background andincreasing contrast between background and alpha-numeric characters insaid image of the label.
 18. The method as claimed in claim 14 whereinimage analysis results are associated with said digitized image andwherein the method further comprises the step of displayingcorresponding image analysis results of the digitized x-ray film. 19.The method as claimed in claim 18 wherein said image analysis is CADanalysis.
 20. A method for automatically grouping digitized x-ray filmscomprising at least one label and belonging to a same case and/orpatient the method comprising the steps of: (i) obtaining a digitalimage of said label; (ii) digitally associating said digitized image ofthe label with said digitized x-ray film; (iii) analyzing images of aplurality of labels associated with respective digitized x-ray films;(iv) identifying labels within said plurality of labels having a desireddegree of correlation sufficient to indicate that said identified labelsbelong to said same case and/or patient; and (v) digitally groupingdigitized x-ray films corresponding to said identified labels.
 21. Themethod as claimed in claim 20 wherein said step or analyzing isperformed using shift/rotation or intensity/contrast variations.
 22. Themethod as claimed in claim 20 wherein each of said identified labels isassociated with each film belonging to said same case and/or patient andwherein any one of said labels can be selected to effect display of allof said films.
 23. A method for assigning a label detection applicationto a digital image the method comprising steps of: (i) selecting a labelacquisition model from a plurality of acquisition models based on atleast one attribute of the digital label; and (ii) selecting a labeldetection application from a plurality of label direction applicationsusing the selected acquisition model.
 24. The method as claimed in claim1 wherein said label is one or more sub-label.
 25. The method as claimedin claim 24 wherein said one or more sub-label comprises informationselected from name of said patient, exposure voltage and orientation.26. The method as claimed in claim 1 wherein said digitized x-ray filmis displayed simultaneously with said label wherein said label anddigitized x-ray film are visually associated.
 27. A system foridentifying and retrieving digitized x-ray films having a label appliedto each film, the system comprising: (i) an x-ray film digitizer forgenerating a digital image of each x-ray film; (ii) means fordetermining a position of the label on the digital image of the x-rayfilm: (iii) means for digitally extracting an image of the label fromthe digital image of the x-ray film; (iv) means for digitallyassociating the image of the label with the digitized image of the x-rayfilm; and (v) means for displaying the label.
 28. The system as claimedin claim 27 further comprising means for digitally associating the labelwith image analysis results of a corresponding digitized image of thex-ray film.
 29. The system as claimed in claim 28 wherein said imageanalysis is CAD analysis.
 30. The system as claimed in claim 28 furthercomprising means for analyzing the images of a plurality of labels. 31.The system as claimed in claim 27 further comprising means fordisplaying images of one or more labels, means for permitting a user toselect one of the displayed labels, means for retrieving a digitizedimage of an x-ray film associated with the selected label and means fordisplaying the retrieved digitized images of the x-ray films forexamination by the user.